Alkylation of hydrocarbons by reducing organic fluoride content of a stream in the operation



Sept. 28, 1965 R. D. BAUER ETAL 3,209,051

ALKYLATION OF HYDROCARBONS BY REDUCING ORGANIC FLUORIDE CONTENT OF ASTREAM IN THE OPERATION Filed April 17, 1962 2 Sheets-sheet 1 O (i I m Zuaddluis U i Ll. D. I

ACCUM,

R. D. BAUER ETAL 3,209,051 ALKYLATION OF HYDROCARBONS BY REDUCINGORGANIC FLUORIDE CONTENT OF A STREAM IN THE OPERATION 2. Sheets-Sheet 2Sept. 28, 1965 Filed April 17, 1962 United States Patent O 3,209,051ALKYLATION F HYDROCARBONS BY REDUC- HNG ORGANIC FLUORIDE CONTENT OF ASTREAM IN THE OPERATION Robert D. Bauer and .loe Van Pool, Bartlesville,Okla., as-

signors to Phillips Petroleum Company, a corporation of Delaware FiledApr. 17, 1962, Ser. No. 188,019 8 Claims. (Cl. 260-683.42)

This invention relates to alkylation of hydrocarbons. In one of itsaspects, it relates to the reduction of organic iluorides in a stream inthe operation by removing the organic fluorides at a place at whichthese have been vfound to tend to concentrate. In another aspect of theinvention, the organic fluorides which have been recovered, as stated,can be returned to the alkylation operation, for example, to thealkylation reactor or settler for further reaction according to methodsnow known or described in copending application of W. E. IPlaster,Serial No. 182,- 847, filed March 27, 1962.

The alkylation of hydrocarbons, for example, the alkylation of anisoparain such as isobutane, with an alkylating agent such as propyleneand/ or butylenes is known. It is also known to alkylate aromatics witholeiins and with olefin-forming materials.

In the recovery of the products resulting from an alkylation in whichpropane is produced, as in the alkylation of isobutane with butylenesand/or propylenes in the presence of hydrouoric acid as catalyst, thereis practiced a removal of propane which otherwise tends to build up inthe operation. Thus, there is fed in such an operation a streamcontaining propane, isobutane and hydrofluoric acid to a propanefractionator, the overhead from which is propane and HF and the bottomsfrom which is isobutane. Heretofore, the alkyl fluorides contained inthe feed fed to the propane fractionator have been distributed in atleast one product removed therefrom. It has now been found that thesealkyl fluorides tend to concentrate in the fractionator reaching amaximum concentration at a :point intermediate the removal of bottomsand the taking off of overhead. Based upon this concept, there is theadditional concept to remove alkyl fluorides from the propanefractionator at a point of maximum fluoride concentration. Thus, a sidecut rich in fluorides is obtained and this can be recycled to thecontactors for alkylation or elsewhere to recover the alkylatableuorides, i.e., the fluorides which will act as alkylating agents. Thefluorides can otherwise be removed as may be desired.

It is an object of this invention to provide an improved alkylationoperation. It is a further object of this invention to reduce thefluoride content of certain streams obtained in the recovery ofeffluents from an alkylation operation. It is a further object of thisinvention to substantially reduce or eliminate after treatment ofcertain streams resulting from a hydrouoric acid alkylation operation,for example, to reduce the size or need lfor so-called bauxitedefluorinators. It is a further object of the invention to reduce thefluoride content of the ultimate hydrocarbon or gasoline product whichare produced by alkylation.

Other aspects, objects and the several advantages of this invention areapparent from a study of this disclosure, the drawing and the appendedclaims.

According to the present invention, alkyl uorides, or other fluorides,are removed from. a point in the operation at which these tend toproduce a maximum concentration. For example, in the alkylation of anisoparaftin with an olefin wherein propane is formed, it is found,according to the invention, that the alkyl iluorides tend to concentrateat a point intermediate the propane overhead removal and the isobutanebottoms of a propane fractionator.

FIGURE 1 lis a schematic diagram of an alkylation proclCC ess wherein,in the fractionation section, the depropanizing has the side drawremoval. The depropanizer has charged thereto the overhead product fromthe deisobutanizing zone.

FIGURE 2 is a schematic diagram of an alkylation process wherein thedepropanizer has the side draw, and a portion of the reactor effluent isthe feed to the depropanizer.

Referring now to the drawing, in FIGURE l, there are passed to analkylation zone 1 by way of 2, 3, and 4, respectively, isobutane, amixture of butylenes and propylene, and hydrogen fluoride. Uponalkylation, the admixture is allowed to settle, forming a lower acidphase which is returned by way of 5 and a hydrocarbon phase which ispassed by 6 into alkylate fractionator 7. In fractionator 7, there isperformed a separation of alkylate removed at 8, obtaining overhead astream containing in addition to some xed gases propane, isobutane andhydrogen fluoride. The overhead passes by 9 into propane fractionator 10from which an isobutane bottoms 11 is obtained. This isobutane isrecycled to alkylator 1 by way of 2. Propane overhead is taken off at12, together with some HF, and sent to the HF stripper 20 for recoveryof propane 21. HF which is recovered is returned for further use in theoperation. P-ropane is flared, recovered as L.P.G., or otherwisedisposed of. According to the invention, there is taken a fluoride-richside cut 13 which, in this instance, is controlled as to flow bycontroller 14 and `control valve 15. The control is so effected as tomaintain in tray 16 a high concentration of fluorides. The removedfluorides, as indicated, are returned to the alkylation reactor or tothe settler or can be disposed of in fuel gas or any other suitableprocessing step. In this embodiment, the iluorides are returned to thealkylation operation.

According to the invention, by providing a plurality of trays asindicated at 17 and 1S, it is possible either during the operation or byprior calculation based upon data to determine just where will be theconcentration of fluoride such that it should be removed from the toweraccording to the invention. If, for any reason, a change of positionoccurs, the plurality of trays'16, 17 and 18 can be operated to yieldthe fluoride stream which is desired to be removed. One skilled in theart in possession of this disclosure, having studied the same, willunderstand how these trays can be operated to remove fluorides whileremoving the least amount of undesired propane. Any isobutane which isremoved with the fluoride stream is helpful in conducting this fluoridestream back to the alkylation or otherwise disposing of the same.Obviously, since it is not desired to waste isobutane, at the very leastthe invention improves the operation by the recovery of the isobutanewhile at the same time reducing the need for extensive treatment of thepropane stream to yrecover lluorides therefrom. By practicing thereduction of uorides, in general, there is obtained a reduction offluoride content in the various streams in which fluoride normallybuilds up and, to this extent, the alkylate is found to be low influoride content with consequent possibility of reduction or eliminationof the after-treaters, `for example. the bauxite defluorinators.

Referring now to FIGURE 2 (to which the example is directed), there arepassed to an alkylation zone 101 by way of 102, 103, and 104,respectively, isobutane, a mixture of butylenes and propylene, andhydrogen fluoride. Upon alkylation, the mixture is allowed to settle,forming a lower acid phase which is returned by way of 105 and ahydrocarbon phase of which a portion is passed by way of conduit 106 andconduit 130 into isobutane stripper 107. The bottoms product 108 fromstripper comprises normal butane and heavier (including alkylate), andthe overhead from 107 is passed by way of conduit 111 as recycledisobutane to the alkylation reaction zone 101. Another portion of thehydrocarbon phase is passed from alkylation zone 101 by way of conduit106 and conduit 109 as feed for depropanizer 110. Bottoms from tower 110is passed by way of conduit 114 and also charged to isobutane stripper107. The overhead yield from depropanizer 110 is charged by way ofconduit 119 and conduit 112 to the propane stripper 120. Propane,substantially free of organic uorides is recovered by way of conduit121. HF which is recovered is recycled to the alkylation zone. Accordingto the invention, there is removed an organic uoride (isopropylfiuoride) -rich side stream 113 which, in this instance is controlled bycontroller 122 and valve 115. The control is effected so as to maintainin tray 116 a high concentration of organic uorides whose rate ofremoval substantially eliminates organic fluorides from the overheadstream 119. The removed fluorides are returned to alkylation, asillustrated, or to any other suitable usage.

According to the invention, a plurality of side draws from trays 116,117, and 11S are available for use, and the selection of the proper traywhere fluoride concentration is the highest is made.

SPECIFIC EXAMPLE lOperation of propane column (110):

Feed temperature, 150 Top temperature, F 130 Sidedraw tray temperature,F 142 Bottom temperature, 220 Reux temperature, 85

Reflux feed volume ratio, 0.744

Tower 110 is a SO-tray tower of 76 percent eiciency. The side draw is onthe forty-third tray from the bottom. The depropanizer overhead issubstantially free of isopropyl fluoride.

DEPROIANIZER COLUMN (110) Mol fraction iC3F in Tray number liquid(Concentration (From bottom) gradient) *The maximum isopropyl fluoridecontent is on the forty-fourth tray.

Conventional operation, saine tower opl-rating conditions STREAM FLOWS,MOLS/HOUR Sido draw (Not used) Overhead (Less reflux) (131) BottomsStream component Feed (109) (114) (0. 05376) 4. 2 Trace Truce TraceTrace 425. 8

Hydrogen luoride Propane Isopropyl iuori Isobntane Normal butaneIsopentane Light alkylate Heavy alkylate Total It has been estimatedthat with the use of this invention there is a savings of approximately$70.00 per day on a 2,000 barrel per day throughput in an alkylationunit in which isobutane is alkylated with isobutylene employinghydrouoric acid as a catalyst. Upon improvement of the separation of theorganic uorides, according to the invention, it appears that eventualcomplete elimination of bauxite deuorinators might well be obtained. Inany event, a great reduction in their use is permitted by practice ofthe invention. The invention is of particular interest at this timesince it now appears that the Natural Gasoline Association of Americawill probably set requirements or specifications for alkylate to containless than 50 parts per million of uorides.

It will be noted that the concept to take advantage of the fact thatuorides will concentrate in the depropanizer appears new in the art.Indeed, the discovery that these uorides will concentrate so that theycan be removed as a side cut from a depropanizer appears to be novel inthe art.

It will be evident to one skilled in the art having studied thisdisclosure, the drawing and the appended claims that there has been setforth a method for alkylating an alkylatable compound with an alkylatingcompound in the presence of hydrouoric acid lwherein organic fluoridesare formed and tend to concentrate in the system which comprises passinga stream containing said Iluorides to a fractionation operation, thereinconcentrating the iluorides, and removing the fluorides from saidfractionation operation.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure, drawing and the appended claims to theinvention the essence of which is that a uoride-rich side stream isremoved from a product stream fractionator, such as a propanefractionator, in the conventional alkylation operation.

We claim:

1. In a method of alkylating in an alkylation reaction zone anisoparaflin with an olefin to produce an alkylate, wherein propane isformed, and wherein hydrofiuoric acid is used as a catalyst, the stepswhich comprise in a irst zone fractionating the alkylate produced toobtain a first alkylate stream and a second stream comprising propane,isobutane, hydrouoric acid and alkyl fluorides, in a second zonefractionating said second stream to obtain overhead comprising propaneand hydrouoric acid vapors and a bottoms product comprising isobutane,in said second zone at an intermediate locus thereof concentrating alkylfluorides, removing from said second zone and from said locus a sidefraction containing said organic uorides which have concentratedtherein, and passing said side fraction to said alkylation reactionzone.

2. In a method of alkylating in an alkylation reaction zone anisoparaiin with an olefin to produce an alkylate, wherein propane isformed, and wherein hydrouoric acid is used as a catalyst, the stepswhich comprise passing an alkylation reaction mass which is obtained toa settling zone, in said settling zone allowing the reaction mass tosettle into at least two phases, an acid phase and a hydrocarbon phase,in a rst zone fractionating the hydrocarbon phase produced to obtain atirst alkylate stream and a second stream containing propane, isobutane,hydroiiuoric acid and alkyl luorides, in a second zone fractionatingsaid second stream to obtain overhead comprising propane and HF and abottoms product comprising isobutane, in said second zone at anintermediate locus thereof concentrating alkyl fluorides, removing fromsaid second zone at said locus a side fraction containing said organiciluorides which are concentrated therein and passing said side fractioninto said settling zone.

3. An improved method for alkylating an isoparaflin and an olefinemploying HF acid catalyst which cornprises contacting said isoparaflinand said olen in presence of said acid in an alkylation reaction zoneforming an alkylation reaction zone eluent, separating an acid phasefrom said elluent, then fractionating said eiuentA to separate analkylate product containing fraction and a second fraction containingunreacted isoparain, paratin, alkyl fluorides and HF, fractionating saidsecond fraction to recover therefrom, as separate fractions, unreactedisoparafiin, parat-lin and HF, and an alkyl fluorides concentrate, andreturning said concentrate to the alkylation reaction.

4. An operation according to claim 3 wherein the isoparaiiin isisobutane and the olefin is at least one olefin selected from the groupconsisting of butylenes and propylene.

5. An improved method for alkylating isoparaiiin and an olefin employingHF acid catalyst which comprises contacting said isoparain and saidolefin in the presence of said acid in an alkylation reaction zoneforming an alkylation reaction zone effluent, in a settling zoneseparating an acid phase from said eiiluent, then fractionating saidefuent to separate an alkylate product containing fraction and a secondfraction containing unreacted isoparaflin, paraffin, alkyl iiuorides andHF, fractionating said second fraction to recover therefrom as separatefractions unreacted isoparafn, paraiiin and HF and an alkyl fluoridesconcentrate, and returning said concentrate to said settling zone.

6. An operation according to claim 5 wherein the isoparaiin is isobutaneand the olefin is at least one olefin selected from the group consistingof butylenes and propylene.

7. An improved method for alkylating an isoparaiiin and an oleiinemploying HF acid catalyst which cornprises contacting said isoparainand said olen in the presence of said acid in an alkylation reactionzone forming an alkylation reaction zone eiiiuent containing low boilingparaiiin, separating an acid phase from said efuent, in a iirstfractionation zone fractionating a portion of said effluent to removetherefrom an alkylate product containing fraction, in a secondfractionation zone fraetionating another portion of said eiuent toseparate therefromV a iirst fraction containing alkylate product andunreacted isoparaflin, a second fraction containing low boiling parainand HF, and a third fraction containing alkyl iiuorides concentratedtherein, which is obtained intermediate said irst and second fractions,and returning said alkyl fluorides to the alkylation operation forfurther reaction therein.

8. A method according to claim 7 wherein said first fraction containingalkylate product and unreacted isoparaflin is passed to said firstfractionation zone.

References Cited by the Examiner UNITED STATES PATENTS 2,347,317 4/44Gibson 260--683.49 2,914,590 11/59 Van Pool 260-683.48 X 3,073,877 l/63Sherk 260-683.48 3,073,878 1/63 Johnson 260-683.48

ALPHONSO D. SULLIVAN, Primary Examiner.

1. IN A METHOD OF ALKYLATING IN AN ALKYLATION REACTION ZONE ANISOPARAFFIN WITH AN OLEFIN TO PRODUCE AN ALKYLATE, WHEREIN PROPANE ISFORMED, AND WHEREIN HYDROFLUORIC ACID IS USED AS A CATALYST, THE STEPSWHICH COMPRISE IN A FIRST ZONE FRACTIONATING THE ALKYLATE PRODUCED TOOBTAIN A FIRST ALKYLATE STREAM AND A SECOND STREAM COMPRISING PROPANE,ISOBUTANE, HYDROFLUORIC ACID AND ALKYL FLUORIDES, IN A SECOND ZONEFRACTIONATING SAID SECOND STREAM TO OBTAIN OVERHEAD COMPRISING PROPANEAND HYDROFLUORIC ACID VAPORS AND A BOTTOMS PRODUCT COMPRISING ISOBUTANE,IN SAID SECOND ZONE AT AN INTERMEDIATE LOCUS THEREOF CONCENTRATING